1. Field of the Invention
The present invention relates in general to the control of illumination of a lamp, and more particularly to an apparatus and a method for controlling the illumination of the lamp, in which the illumination of the lamp is controlled suitably to a condition around the lamp and a high power factor is always maintained regardless of a variation in a load.
2. Description of the Prior Art
Conventional illumination equipments comprise lamp illumination control means which is artificially operable by the user. When an illumination of a lamp is varied with a variation in an ambient illumination or in a commercial alternating current (AC) power, the lamp illumination control means may be operated by the user to control the illumination of the lamp appropriately by raising or lowering it. In this case, the user has the trouble of frequently operating the lamp illumination control means since the ambient illumination and the commercial AC power may be varied at any time.
Also, in the case where the illumination of the lamp is artificially raised by the user because of a variation in a voltage or a low ambient illumination, a lamp drive current is abruptly increased in amount, resulting in generation of a phase difference between the lamp drive current and a lamp drive voltage. The generation of the phase difference makes a power factor bad.
Further, even when the user is absent for a long time, lighting of the lamp is continuously maintained resulting in an unnecessary power consumption.
In order to solve the above problems, there have recently been proposed apparatus for controlling the lighting of the lamp, and one example thereof is disclosed in Japanese Patent Laid-open Publication No. Heisei 2-103897 and is shown in FIG. 1, herein.
As shown in FIG. 1, the conventional lighting control apparatus comprises a human body detecting circuit 112, a power supply circuit 113 and a control circuit 114 to control the lighting of the lamp 111. The human body detecting circuit 112 includes an infrared-ray sensor 115, an amplifier 116 and a level discriminator 117. The infrared-ray sensor 115 senses an infrared-ray in an illumination control area and converts the sensed infrared-ray into a voltage. The amplifier 116 amplifies the output voltage from the infrared-ray sensor 115 by a predetermined level. The level discriminator 117 compares the output voltage from the amplifier 116 with a reference voltage. If the output voltage from the amplifier 116 is higher than the reference voltage in accordance with the compared result, the level discriminator 117 outputs a human body detect signal indicative of the presence of a man in the illumination control area.
The conventional lighting control apparatus has the effect of controlling actuation of the lamp according to the detection of the presence of the user in the illumination control area. However, the conventional lighting control apparatus is desirable to interrupt a power supply path from the power supply circuit, but has the disadvantage that it cannot be applied to a switching mode power supply (SMPS) system.